In many general-illumination light emitting diode lighting applications, such as those for fully visible or ceiling-recessed cylindrical-can fixtures used in retail, architecture or entertainment applications, there is a need to remove substantial heat generated by the high brightness LEDs. In such applications, the light output of a given form factor can be limited, not primarily by the electronic drivers or even the LEDs themselves, but rather by managing the amount of LED-originated heat which can be effectively transferred to the surrounding air from a given volumetric space of the desired fixture or housing.
The amount of heat dissipation which can be tolerated for a given LED power level is determined, to a large degree, by the cumulative thermal resistance from the LED PN junctions to the surrounding air. In reference to the article “Cooling a high density converter impacts performance and reliability”, regarding the multiplicity of thermal resistances which make up the total thermal resistance path, it is the specific thermal resistance from the LED holding substrate to the surrounding air, which is most important for the purposes of the proposed embodiments of this invention. (1)
In conventional designs, LED substrates are attached to a type of heat sink. Without air flow, these heat sinks are often quite large. If inadequately sized or configured incorrectly, the heat sinks are only able to partially fulfill their role, and will provide insufficient amounts of cooling. Others have employed a variety of active-cooling (i.e. convective) methods. Such methods include circulating air with fans or vibration mechanisms to decrease the substrate-to-air thermal resistance. Heat sinks, coupled with some form of active cooling, can improve the thermal resistance characteristics over that with little or no moving air.
The fundamental advantages of using fan cooling to achieve higher power for a given lighting system has been long known in the lighting industry. For many years, companies have been using fans in high power photographic, projection, and theatrical lighting systems.
It is an expressed purpose of the invention to allow the creation of a fully characterized module which can be treated essentially as a purchased product, ready to be incorporated into a light fixture housing. Also, the present invention allows for the creation of a fully characterized module as a very compact, highly predictable, exceptionally efficient, “plug and play” thermal management component, usable over a wide range of operating conditions. Furthermore, the user has the ability to design lighting fixtures with a degree of compactness, which was often not feasible with prior art.